Transmission network



Sept. 12, 1933. w. A. MARRISON TRANSMISSION NETWORK Filed Oct. 23,

FREQUENCY lNl/ENTOR W A. MARE/501V 51 Patented Sept. 12, 1933 1,926,877TRANSMISSION NETWORK Warren A. Marrison, Maplewood, N. J., assignor toBell Telephone Laboratories, Incorporated, New York, N. Y., acorporation of New York -Application October 23,

.6 Claims.

This invention relates to phase controlling networks and has for itsprincipal object controlling the phase of a current without affectingits amplitude. Another object is the economy of electrical elements in aphase shifting network.

The nature of the invention will be most readily understood from thefollowing detailed description and by reference to the attached drawingof which,

Fig. 1 is a theoretical diagram for the explanation of the principle ofthe invention;

Fig. 2 is a schematic diagram of a variable device embodying theinvention; and

Fig. 3 illustrates the phase characteristic of the device of Fig. 2.

In Fig. 1 is shown a generalized symmetrical lattice network havingequal line impedances Z1 and equal lattice impedances Z2. Between onepair of terminals 1, 2 is connected a resistance of value R in serieswith a wave source of voltage E and between the other pair of terminals3, 4 is connected another resistance of equal value. For the symmetricalarrangement shown, the value of the output current I2 in the secondresistance is given by the formula:

In the arrangement shown in Fig. 2, the line impedances Z1 areconstituted by resistances of value R, equal to the terminalresistances, and the lattice impedances Z2 by equal capacities of valueC. For this network the value of the output current is obtainedfromEquation 1 by the substitution and the constant current amplitude by Bymaking the two capacities simultaneously 1931. Serial N0. 570,650

variable so that their values are maintained equal, the phase of theoutput current may be varied without changing its amplitude, the phasebeing advanced as the capacity is increased and vice versa. The totalrange of the phase change as the value or" the capacity is increasedfrom zero to infinity is 1r radians or 180; with a moderate capacityvariation, a large fraction of this change may be accomplished. Inpractice, the capacitiesmay be constituted by similar variable aircondensers mechanically coupled and provided with a single adjustingmeans as indicated schematically in the drawing.

The variation of the phase change with frequency, assuming a fixedadjusting of the capacities is indicated by the curve of Fig. 3 whichshows the phase difierence between the output current and the inputvoltage, plotted as ordinates against frequency as abscissa. Over a widerange of fiow frequencies, the phase displacement is practicallyproportional to the frequency. For other adjustments of the capacities,the linear relation is maintained but'the slope of the characteristic isaltered.

In the arrangement of Fig. 2, the terminal resistances may representportions of an extended telephone line, the characteristic impedance ofwhich is generally a substantially constant resistance. The device maybe used in many other obvious connections, however, where it is desiredto control the phase of a current without varying its amplitude or tocontrol the slope of the phase. characteristic as described above.

The schematic arrangement of Figs. 1 and 2 is shown as a latticenetwork. It is well known that this is a form of Wheatstone bridge, thetwo line branches and the two diagonal arms of the lattice constitutingthe four bridge arms. The term lattice branch is used to define thediagonal arms of the lattice and the term line branch to define theother two branches.

What is claimed is:

1. A phase controlling network comprising, in

combination with equal resistive terminal impedances, a lattice networkhaving a pair of line branches constituted by resistances equal inmagnitude to the resistances of the terminal impedances and latticebranches constituted by equal reactances.

2. A phase controlling network in accordance with claim 1 in which thelattice branch impedances are constituted by equal capacities.

3. A phase controlling network comprising a plurality of impedancebranches arranged in Wheatstone bridge formation, two opposing arms ofthe bridge being constituted by equal resistances and the other twoopposing arms being formed by equal variable reactance elementsmechanically coupled together to maintain equality of the reactances.

4. A phase controlling network in accordance with claim 3 in which thereactance elements are variable condensers.

5. A phase controlling network adapted to operate between equal terminalimpedances of resistance R, comprising a plurality of impedance branchesarranged in Wheatstone bridge forma-

